Perhaps ever since Thomas Alva Edison invented the phonograph in 1876, man has attempted to control the transmission of sound to his advantage. Today, the need for sound control can be found in a variety of different environments and settings. For example, office buildings, doctor's offices, recording studios, home theaters, etc. generally employ various types of materials for preventing the unwanted transmission of sound.
Acoustics is defined as the science that deals with the production, control, transmission, reception and effects of sound. When considering the problem of noise control, one must differentiate between sound absorption, sound insulation, sound reflection and sound diffusion. Sound absorption refers to the attenuation of reverberant noise within the same room or area as the noise source. The sound absorption coefficient of a material is a measure of its ability to absorb noise efficiently. For example, a material that absorbs 100% of the sound energy striking it has a sound absorption coefficient of one.
Sound insulation refers to the reduction of noise being transmitted from one area into another area. The "Sound Reduction Index" or "Transmission Loss" of building elements are terms which described the resistance of that element to airborne sound transmission. The following table compares the degree of acoustic privacy with the sound reduction index:
______________________________________ Sound Reduction Index Hearing Conditions ______________________________________ 35 dB or less Normal speech can be understood quite easily and distinctly through the walls. 35 to 40 Db Loud speech can be understood fairly well. Normal speech can be heard but not easily understood. 40 to 45 dB Loud speech can be heard, but is not easily intelligible. Normal speech can be heard only faintly, if at all. 45 to 50 dB Loud speech can be faintly heard but not understood. Normal speech is inaudible. 55 dB or greater Very loud sounds, such as loud singing, brass musical instruments or a radio at full volume can be heard faintly or not at all. ______________________________________
Sound reflection refers to transmission of sound in another direction by virtue of the sound bouncing off of a non-sound absorbing surface. The sound reflection coefficient of a material is the ratio of the amount of reflected sound energy to that of the incident sound energy striking the material. When tested for sabine absorption in a reverberation room, an absorption coefficient of 0.20 will generally result in a reflection coefficient of 0.90.
Sound diffusion is the uniform distribution or scattering of sound by controlled reflection. This is particularly important in home theaters to ensure that "surround sound" effects are not specifically localized thus producing the unwanted perception of "sound from a box". Thus, to prevent such sound localization, it is desirable to diffuse, or control the reflection of, the sound energy in a range of frequencies.
Over the years, a variety of different materials and apparatuses have been developed for controlling the transmission and absorption of sound based on the foregoing principles. Different forms of acoustical panels have been used in making furniture, room dividers, partitions, wall constructions, ceiling constructions and the like. For example, U.S. Pat. No. 2,081,765 to Prudden discloses an acoustical structure that is generally loosely attached to a wall for preventing the transmission of sound therethrough. Such structure, however, can be difficult and time consuming to install. Because such structure is loosely attached to the wall, it offers no structural support to the wall. Furthermore, such structure cannot be provided in complex surface geometries designed for the advantageous absorption and reflection of sound.
Another acoustical panel is disclosed in U.S. Pat. No. 3,712,846 to Daniels et al. While the Daniels et al. panel includes a rigid main body, the flexible outer covering includes a plurality of projections and indentations that can trap dirt and debris making it difficult to keep clean. Furthermore, such irregular surface may not be aesthetically desirable. Other embodiments in the Daniels et al. panel employ a woven outer covering that may also have similar shortcomings. Other panels which have desirable structural characteristics are disclosed in U.S. Pat. No. 2,692,219 to Slater et al. However, such panels are not well-adapted to be formed with complex geometric surfaces.
U.S. Pat. No. 4,661,392 to Kapstad discloses a sound dampening panel that includes a corrugated center barrier that is sandwiched between fibrous sound dampening material. The sound dampening material is housed within a frame and is covered with a fabric material. Such panel is intended to be used as a partition panel, and thus is not well-suited for attachment to structures such as ceilings, walls, etc.
Another panel structure is disclosed in U.S. Pat. No. 5,606,833 to Andersson. The panel comprises a rigid support sheet that has an insulating sheet attached thereto. Anderson teaches that the insulating sheet of each panel is placed inwardly and not exposed.
U.S. Pat. No. 4,719,730 to Winkowski discloses a demountable partition wall that includes a sound absorbing tack board including a gypsum baseboard, a mineral fiber core board and a porous decorative sheet of material adhered to the core board. The tack board is hung such that the core board faces toward sound and absorbs it.
Decoustics, a company located in Toronto, Canada, also manufactures assorted types of wall panels and ceiling tiles that provide various acoustical properties. Such panels and tiles, however, are not well-adapted for being formed with a variety of geometric surfaces. Thus, in general, many previously proposed acoustical panel constructions are less desirable because they are either too expensive to produce economically, provide poor performance and/or are difficult to install and maintain.
Yet another panel arrangement is disclosed in U.S. Pat. No. 5,606,841 to Carter, Jr. The panels disclosed in that patent comprise interior filled wall panels that include a framed backing member to which an outer sheet material is attached. A filler or padding material that may have desirable thermal or acoustical properties is retained between the backing member and the sheet material. The sheet material is secured through the filler material in a plurality of spaced locations to create a three dimensional surface relief.
U.S. Pat. No. 3,721,050 to Perina discloses a modular grid panel retention system that can be used to cover the walls and/or ceiling surfaces of a room. The system includes 4'.times.8' grid-like sections which may be fastened to the wall, ceiling or support structure by screws, bolts or hook and loop-type fasteners. Each grid-like section includes a plurality of panel receiving cavities for receiving wall panels, ceiling tiles and the like therein. The grid-like structures disclosed in this patent can be cumbersome to handle and install. In addition, the numerous exposed frame portions of each grid-like section can provide undesirable sound reflection in rooms requiring enhanced acoustical properties.
Other diffuser panel arrangements are manufactured by RPG Diffusor Systems, Inc. located at 651-C Commerce Drive, Upper Marlboro, Md. 20774. For example, RPG manufactures a diffuser panel under the trademark Skyline that consists of a panel that has a plurality of outwardly extending columns which provide two-dimensional diffusion. Such panel is adapted to be affixed to an exterior wall or ceiling surface.
In existing wall arrangements, it is generally desirable to mount acoustical diffuser and absorption panels such that they do not occupy any interior space. Thus, it is advantageous to recess such panels within the existing wall structure. To do so, however, the structural integrity of the wall is usually compromised by cutting the wall board and studding. Also, prior acoustical diffuser panels provide little or no structural support to the wall, requiring the installation of additional support braces and cross-studs in the wall. After the additional bracing has been added and the diffuser panels are installed, a discrete cover member is typically installed to cover the opening in the wall. Because such discrete cover does not cover the entire wall it can detract from the overall aesthetic appearance of the wall.
The above-mentioned panels and arrangements due to their cost, have not been embraced by the residential market. Homeowners desiring to acoustically tune a room to enhance the sound performance of their stereo systems usually are prevented from doing so due to the relatively high costs associated with purchasing and installing such materials and devices.
In addition, various methods have been employed to enhance the performance of speakers. For example, U.S. Pat. No. 3,962,544 to Kobayashi discloses a speaker arrangement that includes low and high frequency speakers wherein the high frequency speaker is mounted within its own housing which permits rear cone radiation out of the housing sides. The housing also permits front cone radiation out of the front of the speaker. Kobayashi claims that such arrangement improves radiation efficiency and transient response. The speaker arrangement is designed to be mounted to a buffer board provided in a stand alone enclosure. The speaker arrangement is not particularly well-suited for use in applications wherein it is desirable for the speaker to be completely recessed within a wall cavity.
U.S. Pat. No. 4,566,557 to Laemaitre discloses a flat acoustic diffuser assembly that includes a speaker that is located within an area that is bordered by a frame. A cover is employed to enclose the front of the assembly. The cover acts as a direct wave attenuator so that the front side of the speaker is covered, but its rear side is uncovered so that unattenuated sound waves are emitted from the rear of the speaker. Thus, this arrangement is not particularly well suited for use in connection with speakers that are designed to be installed in a wall cavity.
U.S. Pat. No. 3,557,901 to Young discloses a sound diffuser unit that comprises a plurality of spaced, radially arranged, spoke-like members which lie in a common plane. The unit is constructed to be supported in front of or mounted directly on the front of a speaker. Such arrangement, however, can detract from the aesthetic appearance of the speaker.
Thus, there is a need for an acoustical diffuser arrangement for use with a wide variety of speakers.
There is a further need for a diffuser panel for speakers that can be advantageously used to create a uniform sound field from the speaker and reduce "phase effects" from boundary walls.
There is a need for an acoustical diffuser panel that can be employed to support one or more speakers and achieve a desired acoustical result therefrom.
There is still another need for a diffuser assembly for supporting one or more speakers within an existing or newly constructed wall or ceiling.
Another need exists for acoustical wall and ceiling treatments that have the attributes mentioned above that is customizable in terms of texture and color.
Another need exists for aesthetic, acoustical built-in wall systems.